package org.eclipse.stem.core;

/*******************************************************************************
 * Copyright (c) 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

import org.eclipse.emf.common.util.URI;
import org.eclipse.emf.ecore.EObject;
import org.eclipse.emf.ecore.impl.BasicEObjectImpl;
import org.eclipse.emf.ecore.resource.Resource;
import org.eclipse.emf.ecore.xmi.XMLHelper;
import org.eclipse.emf.ecore.xmi.impl.XMIHelperImpl;
import org.eclipse.emf.ecore.xmi.impl.XMIResourceFactoryImpl;
import org.eclipse.emf.ecore.xmi.impl.XMIResourceImpl;
import org.eclipse.stem.core.common.Identifiable;

/**
 * This class is the {@link XMIResourceFactoryImpl} for the STEM project. It's
 * purpose is to provide an implementation of {@link XMIResourceImpl} whose
 * {@link XMLHelper} has a customized implementation of
 * {@link XMLHelper#getHREF(EObject)} that filters serialized {@link URI}'s such
 * that they remain platform relative (i.e.,
 * "platform:/projectname/foo/bar..."), or if absolute, are deresolved against
 * the {@link Resource}'s {@link URI} so they remain internally relative to the
 * containing file.
 * <p>
 * This is important as the serialized {@link Identifiable}s need to be able to
 * be copied, moved and exported. If their references to other serialized
 * {@link Identifiable}s were relative to file location rather than to the
 * platform, such operations would break the links. Thus, all serialization
 * operations the involve {@link Identifiable}s must employ this class. Look for
 * references to {@link #INSTANCE} so see how this is accomplished.
 */
public class STEMXMIResourceFactoryImpl extends XMIResourceFactoryImpl {

	public static STEMXMIResourceFactoryImpl INSTANCE = new STEMXMIResourceFactoryImpl();

	/**
	 * private so only a singleton instance is created
	 * 
	 * @see #INSTANCE
	 */
	private STEMXMIResourceFactoryImpl() {
		super();
	}

	@Override
	public Resource createResource(URI uri) {
		return new XMIResourceImpl(uri) {
			@Override
			protected XMLHelper createXMLHelper() {
				return new XMIHelperImpl() {
					@Override
					public String getHREF(EObject obj) {
						if (obj instanceof Identifiable) {
							// Yes
							final Identifiable identifiable = (Identifiable) obj;
							final URI uri = identifiable.getURI();
							// Is it a platform URI?
							if (uri.isPlatform()) {
								// Yes
								return uri.toString() + "#/";
							} // if platform URI?

							// Is it an unresolved proxy?
							else if (identifiable.eIsProxy()) {
								// Yes
								return ((BasicEObjectImpl) identifiable)
										.eProxyURI().toString();
							} // if unresolved proxy

							else {
								// No
								// Resolve it against the URI of the
								// identifiable's resource
								deresolve = true;
								resourceURI = identifiable.eResource().getURI();
								return super.getHREF(obj);
							} // else

						} // if Identifiable
						else
							return super.getHREF(obj);
					} // getHREF
				};
			} // createXMLHelper
		};
	} // createResource
} // STEMXMIResourceFactoryImpl